Lately, there is a strong demand to reduce fuel consumption of automobiles in connection with a worldwide effluent control of carbon dioxide associated with a growing interest in environmental problems. In order to cope with such a demand, there is a need to reduce the rolling resistance of a tire. As a means for reducing the rolling resistance of the tire, it is effective to use a rubber composition having a smaller loss tangent (tan δ) and a low heat buildup as a rubber composition applied to a tread portion of the tire.
On the other hand, as a rubber composition applied to the tread portion of the tire, it is preferable that a rubber composition having a high storage modulus (G′). Thus, there is a need for a rubber composition having a low loss tangent (tan δ) and a high storage modulus (G′). In this context, as a means for improving the storage modulus (G′) of the rubber composition, there is a known method wherein an amount of carbon black compounded in the rubber composition is increased, a technique wherein a bismaleimide (BMI) having a specified structure such as N,N′-(4,4′-diphenylmethane)-bismaleimide or the like is compounded as described in JP-A-2002-121326, and a technique wherein a compound having both a reactive group for a rubber component and an adsorption group for a filler such as polyethylene glycol dimaleate (PEGM) or the like is compounded as described in JP-A-2003-176378.